A gas produced in an industrial plant, for example from a refinery, can comprise constituents that are considered to be unwanted during the transportation and/or the use thereof. Such constituents are, by way of non limitative example, acid gases such as CO.sub.2, or H.sub.2 S, or an inert gas such as nitrogen.
A commonly used processing method consists in carrying out an absorption stage by bringing the gas to be processed into countercurrent contact with a solvent in a column, the solvent allowing notably to extract selectively one or more constituents contained in the gas, then in regenerating the solvent by distillation under reduced pressure. Such a method of operation, detailed in FIG. 1, is more particularly suited to remove impurities or at least to separate one or more constituents present in relatively small amounts in the gas. It consists in precooling the gas to be processed and in using a solvent at low temperature to carry out the absorption stage. However, such a process can become costly when the constituent content is high, on account of the necessity of circulating and of distilling large amounts of solvent with a high content of constituents to be separated from the gas to be processed. In fact, distillation of the solvent is generally a relatively expensive operation which requires heating the column at the bottom and cooling it at the top.
A new gas processing method which overcomes the drawbacks of the prior art and which notably allows to decrease the solvent processing cost and the amount necessary to process the gas has been discovered. Such a process is particularly well-suited when the gas constituent(s) is or are present in relatively large proportions.